1 Field of the Invention
The present invention relates to the field of semiconductor wafer processing equipment and, particularly, for use in conjunction with a chemical vapor deposition equipment.
2. Prior Art
In the manufacture of semiconductor integrated circuits, various wafer processing equipment are utilized to fabricate integrated circuit devices on a semiconductor wafer. One such equipment is the deposition machine which is used to deposit one or more of a variety of layers onto the wafer during its fabrication. A variety of deposition equipment are available for depositing such layers as dielectric, metal and polysilicon. One class of such deposition equipment utilizes a chemical vapor deposition (CVD) process to deposit a particular layer onto the wafer. It is preferred that the deposition layer be deposited uniformly onto the wafer.
One particular uniformity problem encountered in depositing a given layer onto the wafer results from pressure fluctuations existing in the exhaust system. That is, during the deposition process, many of the tightly controlled parameters of the equipment are defeated simply due to the fluctuations experienced by the equipment in the exhaust system. This fluctuation is primarily due to the exhaust system of the equipment being coupled to an exhaust system of the semiconductor fabrication plant. Such fluctuations in the exhaust system is further pronounced, if the equipment utilizes an atmospheric pressure chemical vapor deposition (APCVD) process.
Furthermore, during the reaction process, reactive plasma is typically converted to solid particulates which enter the exhaust line of the exhaust system. The particulates tend to adhere to the internal surface of the exhaust system. The trapped solid particulate residue will continue to build in the exhaust lines, posing not only a potential fire hazard, but a long term maintenance problem for the exhaust system. Extensive periodic cleaning is usually required in order to maintain a sufficiently clean exhaust system.